Mariner prop change advice ...

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Volusian

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Hi all ...

I have a Mariner 60 outboard dated approx 1995 .. 3 cyl 2 stroke. The existing prop is marked 48-73138-A40 14P. I've been advised that it is possibly a little undersized for the outboard and that i would benefit from a slightly larger prop ...

What i would like to know is would i benefit from a larger prop and if so what model should i got for ?

thanks
 
Why?
What is the boat and what is the advice based on?
Someone on here will give you good advice.
Peeps need to know what you are trying to achieve.
IE
More speed
Getting on the plane.
Economy etc etc.
Gis a clue!
 
Kawasaki said:
Why?
What is the boat and what is the advice based on?
Someone on here will give you good advice.
Peeps need to know what you are trying to achieve.
IE
More speed
Getting on the plane.
Economy etc etc.
Gis a clue!
Click to expand...

sorry about that ... its on a Wilson Flyer 17 ...

Ive been told that it a larger prop will increase the fuel economy and also a little more speed ...

However im quite happy with its current speed and planing abilities but if it helps fuel economy then all good and well ... providing the prop price isnt too high ..
 
No sweat Volusion.
OK lets talk about speed first.
Your Flyer should reach about 30 kts.
On the rare occasions when the elements will let it!
With a 60 on the blunt end I reckon.
If the hull is clean with a couple of peeps aboard.
How does that relate to your current set up?
Just guessing by the way, based on similar boats I have owned and driven.
 
It's all a bit of a trade off, think of the prop like a gear box. If it feels to be in second, then maybe wise to go to third or fourth. But if already in top gear, any more and your going to go slower. Try some of the prop web sites, that work out the right prop for you. Umm, cant think of them at the moment. Ones steel developments in london I think.
 
Trouble is Hadyn, those prop sights although pretty dam good, like www.castlemarine.co.uk
are better for displacement and semi type boats.
Although there was a Post on ere a few days ago which gave the www of an American mob which dealt specifically in sports boats and the like.

But your 'trade off' theory is quite correct.
Not a bad explanation either for an ex veg salesman!!!!
 
Kawasaki said:
No sweat Volusion.
OK lets talk about speed first.
Your Flyer should reach about 30 kts.
On the rare occasions when the elements will let it!
With a 60 on the blunt end I reckon.
If the hull is clean with a couple of peeps aboard.
How does that relate to your current set up?
Just guessing by the way, based on similar boats I have owned and driven.
Click to expand...


I would say it gets to 30 on occasions as you say .. no more. Hull is clean. Normally 2 on board.

Thing is im quite new to all this and am only mentioning this possible prop upgrade on the strength of other peoples advice recently offered to me. 4 people up to now have mentioned this who have owned boats for quite some time and still do.

So what im asking for is are they possibly correct in saying that i could/would gain better performance and fuel economy by upping the prop size.

One did say that having a larger prop would give greater distance travelled per prop revolution = higher speed at lower revs = better fuel economy ?
 
OK , it seems you have optimum speed set up.
A 'Larger'prop is not the whole answer.
For the best performance.
Prop pitch and diameter have to be taken into consideration.
From your information given (without trawling the net or looking up stuff!) I think the diameter, ie the size of prop is ok for the Flyer.
The 'pitch' however can do various things for you.
Changing the pitch of the prop can give you different a different performance.
OK , She will achieve 30 kts ish you say.
What do you want?
Pull a skier, go fishing, cruise about?
The 'pitch'of the prop, ie the angle of the blades will fine tune the engine/ boat relationship.
Good innit!
 
:confused::confused: i soon will be :confused::confused:

so if you dont increase the size of the prop (blade length) how can one increase the pitch size ? surely the pitch size goes hand in hand with blade curvature length - hence surely a larger diameter prop ? :confused:

i just want the most economical sized prop for the engine / boat combo for getting to my fishing marks as quick as possible with a possible saving on fuel ..
 
OK , so you don't want to go doing watersports etc.
There are two measurements which are significant for props.
The diameter and pitch
The two do not go hand in hand as you put it.
The pitch is the 'angle' of the blades.
The diameter is obvious.
Theoretically the pitch, lets say its a 12inch pitch , for example.
Is the 'theoretical' amount the boat will be shunted forward with each revolution of the prop.
So a 14 will shove the boat 14 inches etc.
This prop lark is a wierd science mate so don't try to understand it in one fell swoop!

Anyway.
Kinda back to hlb's gearbox theory.

Lets say you have a 10 x 14 prop on the boat at the mo
That would mean a 10 inch diameter by 14 Pitch.

If 10 is the correct diameter, not saying it is just guessing again!

If you want to 'take off 'faster you might want to fit a pitch of 15, 16 or maybe 17.
This pitch lark kinda changes the 'gearing'.

OK , whizzing off from a stanstill is ok for skiing etc but not your bag it seems.
To cut through all this bulls hit, if you can plane easily then back the revs off nicely to about 3 thou and scoot along happily, I think that is your target Matey.

Changing diameter is governed by how much room you have, case the prop hits the engine leg!
It is the Pitch you need to change probably, if at all, I would think not the Diameter.

Getting back to basics.
Does She get up on the plane ok with two or three on board and all your kit?
You are not looking for how fast but how economical really I suspect.
3 to 3.5 revs at about 20 kts would seem ideal to Me.
How does that compare with whats going on at the Mo?
 
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